1. Field of Invention
The invention relates to surgical access instruments for use with anterior approach spinal surgery, such as anterior spinal fusion surgery associated with herniated discs and other pathology of the cervical spine, and also for use with other orthopedic surgeries.
2. Background of the Invention
Surgery on structures within a patient often requires the use of retracting devices to hold tissues away from the desired surgical site. Many varieties of surgical retractors exist including devices using tubular probes, using paddle-like extensions, or more complicated mechanical assemblies. Probes and even paddle-like extensions exhibit areas of increased, localized retraction pressure, which can result in tissue damage. Further, with paddle-like, wall-like, and especially tubular-shaped probe retractors, tissue intrudes from non-retracted sides.
Typical retractors are usually not affixed into place relative to bone or other structure. While there has been some progress in designing retractors with the capability of being affixed to bone, such as U.S. Pat. No. 5,027,793 to Engelhardt or U.S. Pat. No. 7,014,608 to Larson, these devices are limited in function and use. The Engelhardt device contemplates the use of spikes, driven into bone, and requires the use of multiple retractors and resection with concomitant trauma to overlying and surrounding tissue.
The Larson device requires the surgeon to first locate, after dissection of the underlying tissue, suitable pedicles on vertebrae for the attachment of guideposts. The guideposts are then attached using an awl or other probe to punch a hole followed by insertion of a screw. The Larson retractor is inserted along these guideposts after which the retaining walls are expanded using a separate expanding device to provide a working area The Larson retractor does not provide means for distraction of underlying, affixed bone. Further, the Larson device retracts from a fully closed state to an open state, using hinges, after introduction of a wedge expander. Expansion while affixed to structure can result in accidental damage to affixed structure from mistranslation of the applied expansion force intended for, as in the Larson device, the mechanically coupled tissue retaining walls. A device that provides retraction prior to insertion of fixation means into bone would be of advantage. A surgeon can more easily locate appropriate fixation sites with such a device and the risk of damage to critical areas such as the spine because of mistranslation of the retraction force would be eliminated.
Other traditional cervical retractors include cylindrical retractors as disclosed in U.S. Pat. No. 6,096,038 of Michelson, conical retractors as disclosed in U.S. Pat. No. 6,896,680 of Michelson or rectangular frame strictures as in U.S. Pat. No. 5,052,373 of Michelson. The devices in these patents are designed for localized use and do not generally separate interfering tissues in the body, such as stemomastoid muscles, nerve, carotid artery, esophagus, or trachea of the neck. Further, as in U.S. Pat. No. 5,052,373 of Michelson, the retraction means utilizes jagged edges to grasp surrounding tissue to prevent expulsion of the retractor. Such means can result in surrounding tissue insult. The combination of factors including interfering tissues in the area of the cervical, thoracic or lumbar spine, and the effects of sharp, blunt edges and limited surface area of traditional retractors also results in limited visualization of surgical sites.
Further, there are no presently known access assemblies that can provide both a means for retraction of tissue and distraction of underlying structure. While distraction devices such as the distractor in U.S. Pat. No. 5,059,194 of Michelson are known. These devices require a separate retraction means. The placement of traditional distractors within the retractor channel occludes the surgeon's view and requires additional intrusions into patient tissue for the separate fixation of the distractor. A device that can function both as a distractor and as a retractor would eliminate the need for separate screws into the vertebral body and would maximize the available space for other surgical instruments. A device such as this would be of benefit.
The present surgical access assembly safely addresses the shortcomings of the presently known instruments. In keeping with the present invention, the objects and design principles of the surgical access assembly of this invention are as follows:                1) to maximize surface area of the retractor, so as to distribute pressure evenly and minimize effective local retraction pressure;        2) to provide a retraction device that allows for prevention of tissue “creep” around the edges of the retractor.        3) to provide a surgical access assembly that can be firmly and safely fixed to the underlying bone so as to obviate tissue intrusion around the working edges of the retractor.        4) to reduce the possibility of accidental over-retraction and thereby avoid carotid, recurrent laryngeal nerve, esophageal and or tracheal damage, in the cervical spine, and to avoid other surrounding tissue insult elsewhere;        5) to allow for binocular vision with the utilization of oblong architecture;        6) to allow for maximal access of light to target tissue, aiding in visualization of said target tissue;        7) to allow for minimization of skin and tissue disruption with the utilization of tapered forward edges or a flange and capture perimeter which spans forward of the incision area;        8) to enable stable retraction fixation to avoid accidental retractor displacement and minimize injury to surrounding structures;        9) to provide retractors which are of lightweight, biocompatible materials to allow for ease of manipulation and safety;        10) to provide transparent retractors to allow for improved visualization of surrounding structures;        11) to provide a retractor which has an adjustable size, particularly an adjustable access channel diameter;        12) to provide a retractor which can affix into bone or tissue and function to distract segments of affixed bone or tissue; and/or,        13) other objects that become apparent from the following descriptions and discussion of the present invention.        
One or more of the above objects is met in whole or in part by the various embodiments of this invention.